1. Field of the Invention
The present invention is related with an optical recording medium. More specifically, it is related with an optical recording medium, to which an analog signal can be recorded, and which can be reproduced by, for example, a LD (Laser Disc) player on the market.
2. Description of the Related Art
In recent years, an optical recording medium, onto which signals can be written once and which can be reproduced by a so-called CD (Compact Disc) player for public use, is marketed. Generally, a cyanine dye is used for the recording film of such a writable optical recording medium of CD type. A digital signal is recorded as a record signal to this type of recording medium.
On the other hand, commercialization of a writable recording medium, as for a so-called LD (Laser Disc) onto which analog signals, such as an image signal and a voice signal, are to be recorded, is also demanded, as in the case of the above-mentioned CD.
However, if an analog signal is recorded by use of a semiconductor laser on the recording film using a cyanine dye as composition of the recording film in the LD recording medium, the sensitivity runs short due to a high linear velocity. Therefore, recording cannot be performed by use of a practical power in this case. Moreover, unlike the case of a digital signal, the influence of a jitter etc. cannot be disregarded in this case. Therefore, as image recording technique, the above-mentioned technique cannot be put into a practical use.
On the other hand, there is another method of image recording, which employs a gas laser of a relatively short wavelength and relatively high output level, and a composite recording film of an aniline series dye and a binder. According to this method, recording can be performed satisfactorily to some extent. However, a recording apparatus becomes very large-scale in this case. Therefore, the possibility to commercialize this method, is very little.